CN114818412B - High-precision calculation method for electromagnetic radiation of human brain - Google Patents
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Abstract
The invention discloses a high-precision calculation method for electromagnetic radiation of human brain, which comprises the following steps: s1, defining a human brain model, namely simulating a biological tissue structure in the brain model by mainly considering the size of the human brain model, and giving corresponding electromagnetic parameter values to the biological tissue according to the characteristics of an electromagnetic environment in which the brain model is positioned; s2, after the definition of the human brain model is completed, mesh subdivision is performed on the target model by using an FCC mesh: in the subdivision process, firstly, the size of a grid is set according to the characteristics of a model, and then the position of each electromagnetic field node is determined; s3, initializing parameters in a field value iteration process after the model is subdivided by using the FCC grid, and S4, initializing parameters in an absorption layer; s5, after the parameters of the absorption layer are set, setting the time step length
An iterative calculation of the electromagnetic field value is performed. The method and the device can evaluate and analyze the possible risks of the human brain exposed in the electromagnetic environment, and ensure the calculation precision of the electromagnetic radiation energy absorption of the human brain.
Description
Technical Field
The invention relates to electromagnetic radiation, in particular to a high-precision calculation method for electromagnetic radiation received by a human brain.
Background
Aiming at radio frequency electromagnetic environments widely existing in daily life, such as the situation of using a mobile phone to surf the internet, using a telephone and the like to expose human tissues to electromagnetic radiation in a short distance for a long time, the potential threat to the human health is caused. Accurate assessment of electromagnetic energy absorption by biological tissue is of great significance for measuring the electromagnetic safety of a living being.
The Finite Difference Time Domain (FDTD) method utilizes a difference equation to process a rotation equation in a Maxwell equation set, and solves the electromagnetic problem from the time domain perspective. Therefore, the FDTD method has natural advantages when applied to dispersive media, such as biological tissues, plasmas and radar absorbing materials. The calculation accuracy of the traditional FDTD method is mainly limited by numerical dispersion errors. The FCC-FDTD method based on the face center grid (FCC) adopts a unit cell structure similar to SiC in chemistry, and reduces the numerical dispersion error of the traditional FDTD method from the basic unit cell angle. However, in order to evaluate the brain model by the FCC-FDTD method, an efficient and highly precise absorption boundary needs to be developed, so that the potential risk of the electromagnetic radiation to the human brain is analyzed by the FCC-FDTD method in a limited computational memory.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, provides a high-precision calculation method for electromagnetic radiation of human brain, evaluates and analyzes the possible risks of the human brain exposed in the electromagnetic environment, and ensures the calculation precision of the electromagnetic radiation energy absorption of the human brain.
The purpose of the invention is realized by the following technical scheme: a high-precision calculation method for electromagnetic radiation of a human brain comprises the following steps:
s1, defining a human brain model, namely simulating a biological tissue structure in the brain model by mainly considering the size of the human brain model, and giving corresponding electromagnetic parameter values to the biological tissue according to the characteristics of an electromagnetic environment in which the brain model is positioned;
further, in step S1, according to the frequency value in the electromagnetic environment characteristic, corresponding electromagnetic parameter values are given to the biological tissue, where the electromagnetic parameter values include a dielectric constant value and a magnetic permeability value.
The process of assigning the corresponding electromagnetic parameter value to the biological tissue in step S1 includes:
s101, pre-establishing a frequency and electromagnetic parameter correspondence table based on biological tissues, wherein the table comprises a plurality of frequencies, and a dielectric constant value and a magnetic permeability value corresponding to each frequency;
s102, according to the frequency of the electromagnetic environment where the brain model is located, corresponding dielectric constant values and magnetic permeability values are searched from the corresponding table and are given to the biological tissue.
S2, after the definition of the human brain model is completed, mesh subdivision is performed on the target model by using an FCC mesh: in the subdivision process, firstly, the size of a grid is set according to the characteristics of a model, and then the position of each electromagnetic field node is determined;
further, in step S2, the position of the electromagnetic field node includes an electric field node coordinate and a magnetic field node coordinate;
let the grid sizes be Deltax, Deltay, Deltaz, and the FCC grid coordinate be (i) s Δx，j s Δy，k s Δ z), where Δ i (i ═ x, y, z) is the size of the FCC grid in the i direction; i all right angle s ，j s ，k s The number of the current grid in the x, y and z directions;
the distributed coordinates of the four electric field nodes are respectively as follows:
E 1 ＝(i s Δx，j s Δy，k s Δz)
E 2 ＝((i s +0.5)Δx，(j s +0.5)Δy，k s Δz)
E 3 ＝((i s +0.5)Δx，j s Δy，(k s +0.5)Δz)
E 4 ＝(i s Δx，(j s +0.5)Δy，(k s +0.5)Δz)
the coordinates of the four magnetic field nodes distributed in the grid are respectively as follows:
s3, after the model is subdivided by using the FCC grid, initializing parameters in a field value iteration process;
further, the initializing content in step S3 includes: initializing four electric field values and four magnetic field values of the whole calculation area to be zero;
and according to the frequency value of the environment where the human brain model is located, determining the type of the radiation source:
establishing a corresponding table of frequency values and radiation source types in advance, wherein the table comprises a plurality of frequencies and the radiation source type corresponding to each frequency; each type of radiation source has a known time domain waveform and excitation duration;
according to the frequency value of the environment where the human brain model is located, the corresponding radiation source type is searched from the corresponding table of the frequency value and the radiation source parameter, and the time domain waveform and the excitation duration of the radiation source are determined.
And S4, initializing parameters in the absorption layer after the calculation area is initialized.
Further, the key of step S4 is to determine the distance from each electromagnetic field node in each grid in the absorbing layer to the absorbing layer and to the interface of the calculation region;
the step S4 includes the following sub-steps:
s401, initializing the distance from a magnetic field node in an absorption layer to the absorption layer and an interface; the four types of magnetic field nodes have two types of distances from the absorption layer to the interface of the calculation region, wherein the distances are rho m，1 (k)＝(k-0.25)Δi，ρ m，2 (k) (k-0.75) Δ i, where ρ m，1 (k)、ρ m，2 (k) The distance from the magnetic field node to the interface of the absorption layer and the calculation region is shown, and k represents the grid number from the magnetic field node to the interface of the absorption layer and the calculation region;
s402, initializing the distance from an electric field node in the absorption layer to the absorption layer and an interface; the four types of electric field nodes have two distances to the interface between the absorption layer and the calculation region, wherein the distances are rho e，1 (k)＝kΔi，ρ e，2 (k)＝(k-0.5)Δi，ρ e，1 (k)、ρ e，2 (k) And (b) representing the distance from the electric field node to the interface of the absorption layer and the calculation region, wherein k represents the number of grids from the electric field node to the interface of the absorption layer and the calculation region.
And S5, after the parameters of the absorption layer are set, setting the time step delta t, and performing iterative calculation on the electromagnetic field value.
Further, the step S5 includes:
s501, setting timeStep length delta t, n is the iteration step number at the current moment, and at the moment of (n +0.5) delta t, the magnetic field values in the calculation area and the absorption layer are updated, and for the first-class magnetic field node H 1 The iterative calculation formula is calculated as follows:
where μ is the magnetic permeability,
and
the calculation mode of the sum depends on the magnetic field node H in the FCC grid 1 The node distribution mode of the electric field surrounding the periphery;
four types of magnetic field node H 1 ～H 4 Only differences of the corner marks exist in the calculation iteration formula of (2), and for H 2 ～H 4 When performing the iteration, according to H 1 The calculation method of (2) is carried out, and the lower corner mark is replaced;
s502, after updating the magnetic field values in the calculation area and the absorption layer, updating the magnetic field of the absorption layer again; when the absorption layer is arranged in the x direction, H in the absorption layer in the x direction needs to be adjusted y ，H z Carrying out updating calculation; when the y-direction is provided with the absorption layer, H in the y-direction absorption layer needs to be adjusted x ，H z Carrying out updating calculation; when an absorption layer is arranged in the z direction, H in the absorption layer in the z direction needs to be adjusted x ，H y Performing update calculation according to a given magnetic field node;
absorption layer magnetic field node H 1 ～H 4 Is calculated over the stackThe formula only has the difference of corner marks, and the node H of the first type of magnetic field 1 The iterative calculation formula is calculated as follows:
kappa is an absorption layer parameter; for H in the absorption layer 2 ～H 4 According to H 1 The calculation method of (2) is carried out, and the subscript is replaced during calculation,
and
is a node H in the absorption layer for the first type of magnetic field 1 A process quantity of iterative update; h in the absorption layer 2 ～H 4 The process quantity of the iterative update is
According to the marked coordinates of the magnetic field nodes and the surfaces from the magnetic field nodes to the absorption layer and the calculation area respectively, the magnetic field nodes are calculated
Divided into two classes and represented by rho m，1 And ρ m，2 Determining; in the absorption layer in the x-direction
And
from rho m，1 And the type of magnetic field node, and,
and
from rho m，2 And magnetic field node type determination; in the absorption layer in the y-direction
And
from rho m，1 And the type of magnetic field node to determine,
and
from rho m，2 And magnetic field node type determination; in the absorption layer in the z-direction
And
from rho m，1 And the type of magnetic field node to determine,
and
from rho m，2 And magnetic field node type determination;
by rho m，1 Determined by the nodes of the magnetic field of the first kind
The calculation formula of (a):
wherein alpha is m，1 ，σ m，1 And kappa m，1 Is the absorption layer parameter and is represented by p m，1 The determination and calculation method are as follows
Wherein sigma max ，α max ，κ max And n cpml Is the absorption layer fixed constant, δ is the absorption layer grid number times this grid step;
due to the similarity of the way in which the calculations are made,
and
relative to
Only the orientation of the lower corner mark needs to be modified,
the calculation can be completed only by replacing the lower corner mark number;
s503, after the magnetic field is processed, updating electric field values in the calculation area and the absorption layer at the (n +1) delta t moment;
epsilon is a dielectric constant of the glass or ceramic,
and
the calculation mode of (2) depends on the distribution mode of the magnetic field nodes surrounding the electric field nodes of the current iteration in the FCC grid;
s504, after the electric field values in the calculation area and the absorption layer are updated, updating the electric field of the absorption layer again; magnetic field node types for two distances; when the absorption layer is arranged in the x direction, the absorption layer is required to be absorbed by E in the absorption layer y ，E z Carrying out updating calculation; when the absorption layer is arranged in the y direction, it is necessary to absorb E in the absorption layer x ，E z Carrying out updating calculation; when an absorbing layer is arranged in the z direction, it is necessary to absorb E in the absorbing layer x ，E y Carrying out updating calculation; for electric field node E of the first kind 1 The iterative calculation mode is as follows:
for the absorption layer E 2 ～E 4 According to the calculation mode of E 1 The calculation method of (2) and the substitution is carried out at the lower corner mark,
and
is a node E in the absorption layer for the first type of magnetic field 1 Iteratively updating the process quantity; in the absorption layer E 2 ～E 4 The process quantity of the iterative update is
According to the marked coordinates of the electric field nodes and the interfaces from the electric field nodes to the absorption layer and the calculation area, the electric field nodes are connected with the absorption layer and the calculation area
Are divided into two classes and represented by rho e，1 And ρ e，2 Determining; in the absorption layer in the x-direction
And
from rho e，1 And the electric field node type decision,
and
from rho e，2 And electric field node type determination; in the absorption layer in the y-direction
And
from rho e，1 And the electric field node type decision,
and
from rho e，2 And electric field node type determination; in the absorption layer in z-direction
And
from rho e，1 And the electric field node type decision,
and
from rho e，2 And electric field node type determination;
by rho e，1 Determined by the nodes of the electric field of the first kind
The calculation formula of (a):
wherein alpha is e，1 ，σ e，1 And kappa e，1 Is the absorption layer parameter and is represented by p e，1 The determination and calculation method are as follows
Due to the similarity of the way in which the calculations are made,
and
relative to
Only the orientation of the lower corner mark needs to be modified,
the calculation can be completed only by replacing the lower corner mark number;
s505, changing the time step from n time to n +1 time, outputting the current time step iteration result, and outputting the electromagnetic field value at the current time recording point, namely the electromagnetic radiation received by the human brain;
and judging whether the maximum value of the set iteration steps is reached, if not, returning to the step S501 to calculate the electromagnetic field value in a new round, and if so, stopping the calculation.
The invention has the beneficial effects that: the invention uses the FCC-FDTD method based on the FCC-CPML absorption boundary to analyze the electromagnetic radiation of the human brain model, and derives the FCC-CPML boundary suitable for the FCC-FDTD method from the FCC-FDTD method. The FCC-CPML boundary can ensure that the FCC-FDTD method uses limited calculation space, and electromagnetic waves do not reflect and penetrate through the boundary in the calculation analysis of electromagnetic radiation of a human brain model for a long time, so that the calculation precision of the electromagnetic radiation energy absorption of the human brain is ensured.
Drawings
FIG. 1 is a flow chart of a method of the present invention;
FIG. 2 is a schematic diagram of a human brain model and mesh generation in an embodiment;
FIG. 3 is a diagram illustrating calculation of electromagnetic energy absorbed by a human brain model according to the FDTD method in an embodiment;
FIG. 4 is a graph illustrating the calculation of electromagnetic energy absorbed by a human brain model according to the FCC-FDTD method based on the FCC-CPML absorption boundary in the example.
Detailed Description
The technical solutions of the present invention are further described in detail below with reference to the accompanying drawings, but the scope of the present invention is not limited to the following.
As shown in fig. 1, a method for calculating the electromagnetic radiation of the human brain with high precision includes the following steps:
s1, defining a human brain model: mainly considering the size of a human brain model, simulating a biological tissue structure in the brain model, and giving corresponding electromagnetic parameter values to the biological tissue according to the characteristics of the electromagnetic environment in which the brain model is positioned;
further, in step S1, according to the frequency value in the electromagnetic environment characteristic, corresponding electromagnetic parameter values are given to the biological tissue, where the electromagnetic parameter values include a dielectric constant value and a magnetic permeability value.
The process of assigning the corresponding electromagnetic parameter value to the biological tissue in step S1 includes:
s101, pre-establishing a frequency and electromagnetic parameter correspondence table based on biological tissues, wherein the table comprises a plurality of frequencies, and a dielectric constant value and a magnetic permeability value corresponding to each frequency;
s102, according to the frequency of the electromagnetic environment where the brain model is located, corresponding dielectric constant values and magnetic permeability values are searched from the corresponding table and are given to the biological tissue.
S2, after the definition of the human brain model is completed, mesh generation is carried out on the target model by using FCC meshes: in the subdivision process, firstly, the size of a grid is set according to the characteristics of a model, and then the position of each electromagnetic field node is determined;
further, in step S2, the position of the electromagnetic field node includes an electric field node coordinate and a magnetic field node coordinate;
let the grid sizes be Deltax, Deltay, Deltaz, and the FCC grid coordinate be (i) s Δx，j s Δy，k s Δ z), where Δ i (i ═ x, y, z) is the size of the FCC grid in the i direction; i.e. i s ，j s ，k s The number of the current grid in the x, y and z directions;
the distributed coordinates of the four electric field nodes are respectively as follows:
E 1 ＝(i s Δx，j s Δy，k s Δz)
E 2 ＝((i s +0.5)Δx，(j s +0.5)Δy，k s Δz)
E 3 ＝((iS+0.5)Δx，j s Δy，(k s +0.5)Δz)
E 4 ＝(i s Δx，(j s +0.5)Δy，(k s +0.5)Δz)
the coordinates of the four magnetic field nodes distributed in the grid are respectively as follows:
s3, after the model is subdivided by using the FCC grid, initializing parameters in a field value iteration process;
further, the initializing content in step S3 includes: initializing four electric field values and four magnetic field values of the whole calculation area to be zero;
and according to the frequency value of the environment where the human brain model is located, determining the type of the radiation source:
establishing a corresponding table of frequency values and radiation source types in advance, wherein the table comprises a plurality of frequencies and the radiation source type corresponding to each frequency; each type of radiation source has a known time domain waveform and excitation duration;
according to the frequency value of the environment where the human brain model is located, the corresponding radiation source type is searched from the corresponding table of the frequency value and the radiation source parameter, and the time domain waveform and the excitation duration of the radiation source are determined.
And S4, initializing parameters in the absorption layer after the calculation area is initialized.
Further, the key to step S4 is to determine the distance from each electromagnetic field node in each grid in the absorber layer to the absorber layer and the interfaces of the calculation region;
the step S4 includes the following sub-steps:
s401, initializing the distance from a magnetic field node in an absorption layer to the absorption layer and an interface; the four types of magnetic field nodes have two types of distances from the absorption layer to the interface of the calculation region, wherein the distances are rho m，1 (k)＝(k-0.25)Δi，ρ m，2 (k) (k-0.75) Δ i, where ρ m，1 (k)、ρ m，2 (k) The distance from the magnetic field node to the interface of the absorption layer and the calculation region is shown, and k represents the grid number from the magnetic field node to the interface of the absorption layer and the calculation region;
s402, initializing the distance from an electric field node in the absorption layer to the absorption layer and an interface; the four types of electric field nodes have two distances to the interface between the absorption layer and the calculation region, wherein the distances are rho e，1 (k)＝kΔi，ρ e，2 (k)＝(k-0.5)Δi，ρ e，1 (k)、ρ e，2 (k) Represents the distance of the electric field node from the interface of the absorption layer and the calculation region, wherein k represents the number of grids from the electric field node to the interface of the absorption layer and the calculation region.
And S5, after the parameters of the absorption layer are set, setting the time step delta t, and performing iterative calculation on the electromagnetic field value.
Further, the step S5 includes:
s501, setting a time step length delta t, wherein n is the number of iteration steps at the current moment, updating magnetic field values in a calculation area and an absorption layer at the moment of (n +0.5) delta t, and aiming at a first-class magnetic field node H 1 The iterative calculation formula is calculated as follows:
where μ is the magnetic permeability,
and
the calculation mode of the sum depends on the magnetic field node H in the FCC grid 1 The distribution mode of the electric field nodes surrounding the periphery;
four types of magnetic field node H 1 ～H 4 Only differences of the corner marks exist in the calculation iteration formula of (2), and for H 2 ～H 4 When performing the iteration, according to H 1 The calculation method of (2) is carried out, and the lower corner mark is replaced;
s502, after updating the magnetic field values in the calculation area and the absorption layer, updating the magnetic field of the absorption layer again; when the absorption layer is arranged in the x direction, H in the absorption layer in the x direction needs to be adjusted y ，H z Carrying out updating calculation; when the y-direction is provided with the absorption layer, H in the y-direction absorption layer needs to be adjusted x ，H z Carrying out updating calculation; when an absorption layer is arranged in the z direction, H in the absorption layer in the z direction needs to be adjusted x ，H y Performing update calculation according to a given magnetic field node;
absorption layer magnetic field node H 1 ～H 4 Only the difference of the corner marks exists in the calculation iteration formula of (1), and the node H is used for the first type of magnetic field 1 The iterative calculation formula is calculated as follows:
kappa is an absorption layer parameter; for H in the absorption layer 2 ～H 4 According to H 1 The calculation method of (2) is carried out, and the subscript is replaced during calculation,
and
is a node H in the absorption layer for the first type of magnetic field 1 Iteratively updating the process quantity; h in the absorption layer 2 ～H 4 The process quantity of the iterative update is
According to the marked coordinates of the magnetic field nodes and the surfaces from the magnetic field nodes to the absorption layer and the calculation area respectively, the magnetic field nodes are calculated
Divided into two classes and represented by rho m，1 And ρ m，2 Determining; in the absorption layer in the x-direction
And
from rho m，1 And the type of magnetic field node to determine,
and
from rho m，2 And magnetic field node type determination; in the absorption layer in the y-direction
And
from rho m，1 And the type of magnetic field node to determine,
and
from rho m，2 And magnetic field node type determination; in the absorption layer in z-direction
And
from rho m，1 And the type of magnetic field node to determine,
and
from rho m，2 And magnetic field node type determination;
by rho m，1 Determined by the nodes of the magnetic field of the first kind
The calculation formula of (a):
wherein alpha is m，1 ，σ m，1 And kappa m，1 Is the absorption layer parameter and is represented by p m，1 The determination and calculation method are as follows
Wherein sigma max ，α max ，κ max And n cpml Is the absorption layer fixed constant, δ is the absorption layer grid number times this grid step;
due to the similarity of the way in which the calculations are made,
and
relative to
Only the orientation of the lower corner mark needs to be modified,
the calculation can be completed only by replacing the lower corner mark number;
s503, after the magnetic field is processed, updating electric field values in the calculation area and the absorption layer at the (n +1) delta t moment;
epsilon is a dielectric constant of the glass or ceramic,
and
the calculation mode of (2) depends on the distribution mode of the magnetic field nodes surrounding the electric field nodes of the current iteration in the FCC grid;
s504. after the electric field values in the calculation area and the absorption layer are updatedUpdating the electric field of the absorption layer again; magnetic field node types for two distances; when the absorption layer is arranged in the x direction, the absorption layer is required to be absorbed by E in the absorption layer y ，E z Carrying out updating calculation; when the absorption layer is arranged in the y direction, it is necessary to absorb E in the absorption layer x ，E z Carrying out updating calculation; when an absorbing layer is arranged in the z direction, it is necessary to absorb E in the absorbing layer x ，E y Carrying out updating calculation; for electric field node E of the first kind 1 The iterative calculation mode is as follows:
for the absorption layer E 2 ～E 4 According to E 1 The calculation method of (2) and the substitution is carried out at the lower corner mark,
and
is a node E in the absorption layer for the first kind of magnetic field 1 Iteratively updating the process quantity; in the absorption layer E 2 ～E 4 The process quantity of the iterative update is
According to the marked coordinates of the electric field nodes and the interfaces from the electric field nodes to the absorption layer and the calculation area, the electric field nodes are connected with the absorption layer and the calculation area
Are divided into two classes and represented by rho e，1 And ρ e，2 Determining(ii) a In the absorption layer in the x-direction
And
from rho e，1 And the electric field node type decision,
and
from rho e，2 And electric field node type determination; in the absorption layer in the y-direction
And
from rho e，1 And the electric field node type decision,
and
from rho e，2 And electric field node type determination; in the absorption layer in z-direction
And
from rho e，1 And the electric field node type decision,
and
from rho e，2 And electric field node type determination;
by rho e，1 And a firstDetermined by the electric field-like node
The calculation formula of (a):
wherein alpha is e，1 ，σ e，1 And kappa e，1 Is the absorption layer parameter and is represented by p e，1 The determination and calculation method are as follows
Due to the similarity of the way in which the calculations are made,
and
relative to
Only the orientation of the lower corner mark needs to be modified,
the calculation can be completed only by replacing the lower corner mark number;
s505, changing the time step from n time to n +1 time, outputting the current time step iteration result, and outputting the electromagnetic field value at the current time recording point, namely the electromagnetic radiation received by the human brain;
and judging whether the maximum value of the set iteration steps is reached, if not, returning to the step S501 to calculate the electromagnetic field value in a new round, and if so, stopping the calculation.
The present application is further illustrated by the following specific examples:
fig. 2 shows a human brain model that takes into account a four-layer medium, and analyzes the electromagnetic energy absorbed by the human brain model over a time-domain period when the handset is communicating using 900 MHz. The human brain model consisted of four biological tissues, skin (thickness: 4cm), fat (thickness: 4cm), bone (thickness: 8cm) and one of the biological tissues inside the human brain (thickness: 92cm) averaged. Consider a human brain model subdivided using an FCC grid size of 2cm x 2 cm. The method for calculating the high-precision electromagnetic radiation on the human brain comprises the following specific steps:
the method comprises the following steps: and defining, subdividing and initializing the FCC mesh.
Step two: the radiation source form of the mobile phone using 900MHz communication is determined. In order to better simulate the communication of a mobile phone by 900MHz, the embodiment uses the following radiation sources to replace the mobile phone
Wherein τ is t/(4 π/ω). The radiation source firstly goes through two gradual change periods to reach a steady state, and electromagnetic energy absorbed by the brain model in the last period is calculated after four periods of steady state operation.
Step three: based on an FCC grid, carrying out finite difference transformation processing on a Maxwell equation set in a time domain to obtain the distribution of an electromagnetic field in a space.
Step four: and carrying out post-processing on the obtained electromagnetic field value in the calculation period. After obtaining the value of the electromagnetic field in one radiation period of the radiation source, we use the following formula:
electromagnetic energy absorbed by the human brain model in a radiation cycle is obtained. FIG. 3 is electromagnetic energy absorbed by a human brain model during a radiation cycle using a conventional FDTD approach, the maximum amount of electromagnetic energy absorbed by the brain model being P max ＝0.2453W/m 3 . FIG. 4 shows the absorption of biological electromagnetic energy by a human brain model with a maximum value of electromagnetic energy absorbed P during a radiation cycle, obtained using the FCC-FDTD method based on FCC-CPML absorption boundaries max ＝0.2024W/m 3 . The exact result of using the power series to calculate the maximum of the electromagnetic energy absorbed by the brain model is P max ＝0.1527W/m 3 . The calculation accuracy improved by the method provided by the patent is 46.33% compared with the traditional method.
While the foregoing description shows and describes a preferred embodiment of the invention, it is to be understood, as noted above, that the invention is not limited to the form disclosed herein, but is not intended to be exhaustive or to exclude other embodiments and may be used in various other combinations, modifications, and environments and may be modified within the scope of the inventive concept described herein by the above teachings or the skill or knowledge of the relevant art. And that modifications and variations may be effected by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (5)
1. A high-precision calculation method for electromagnetic radiation of a human brain is characterized by comprising the following steps: the method comprises the following steps:
s1, defining a human brain model: the method mainly considers the size of a human brain model, simulates the biological tissue structure in the brain model, and gives corresponding electromagnetic parameter values to the biological tissue according to the electromagnetic environment characteristics of the brain model;
in step S1, according to the frequency value in the electromagnetic environment characteristic, giving a corresponding electromagnetic parameter value to the biological tissue, where the electromagnetic parameter value includes a dielectric constant value and a permeability value;
the process of assigning the corresponding electromagnetic parameter value to the biological tissue in step S1 includes:
s101, pre-establishing a frequency and electromagnetic parameter correspondence table based on biological tissues, wherein the table comprises a plurality of frequencies, and a dielectric constant value and a magnetic permeability value corresponding to each frequency;
s102, according to the frequency of the electromagnetic environment where the brain model is located, corresponding dielectric constant values and magnetic permeability values are searched from a corresponding table and are given to biological tissues;
s2, after the definition of the human brain model is completed, mesh generation is carried out on the target model by using FCC meshes: in the subdivision process, firstly, the size of a grid is set according to the characteristics of a model, and then the position of each electromagnetic field node is determined;
s3, after the model is subdivided by using the FCC grid, initializing parameters in a field value iteration process;
s4, initializing parameters in the absorption layer after the calculation area is initialized;
and S5, after the parameters of the absorption layer are set, setting a time step delta t, and performing iterative calculation on the electromagnetic field value.
2. A method for calculating the electromagnetic radiation exposure of the human brain according to claim 1, wherein: in step S2, the position of the electromagnetic field node includes an electric field node coordinate and a magnetic field node coordinate;
let the grid size be Δ x, Δ y, Δ z, and FCC grid coordinate be (i) s Δx，j s Δy，k s Δ z), where Δ i (i ═ x, y, z) is the size of the FCC grid in the i direction; i.e. i s ，j s ，k s The number of the current grid in the x, y and z directions;
the distributed coordinates of the four electric field nodes are respectively as follows:
E 1 ＝(i s Δx，j s Δy，k s Δz)
E 2 ＝((i s +0.5)Δx，(j s +0.5)Δy，k s Δz)
E 3 ＝((i s +0.5)Δx，j s Δy，(k s +0.5)Δz)
E 4 ＝(i s Δx，(j s +0.5)Δy，(k s +0.5)Δz)
the coordinates of the four magnetic field nodes distributed in the grid are respectively as follows:
3. a method for calculating the electromagnetic radiation exposure of the human brain according to claim 1, wherein: the initialization content in step S3 includes: initializing four electric field values and four magnetic field values of the whole calculation area to be zero;
and according to the frequency value of the environment where the human brain model is located, determining the type of the radiation source:
establishing a corresponding table of frequency values and radiation source types in advance, wherein the table comprises a plurality of frequencies and the radiation source type corresponding to each frequency; each type of radiation source has a known time domain waveform and excitation duration;
according to the frequency value of the environment where the human brain model is located, the corresponding radiation source type is searched from the corresponding table of the frequency value and the radiation source parameter, and the time domain waveform and the excitation duration of the radiation source are determined.
4. A method for calculating the electromagnetic radiation in the human brain with high accuracy according to claim 1, wherein: the key to step S4 is determining the distance from each electromagnetic field node in each grid in the absorber layer to the absorber layer and the interface of the calculation region;
the step S4 includes the following sub-steps:
s401, initializing the distance from a magnetic field node in an absorption layer to the absorption layer and an interface; the four types of magnetic field nodes have two types of distances from the absorption layer to the interface of the calculation region, wherein the distances are rho m，1 (k)＝(k-0.25)Δi，ρ m，2 (k) (k-0.75) Δ i, where ρ m，1 (k)、ρ m，2 (k) Denotes the distance from the magnetic field node to the interface between the absorption layer and the calculation region, and k denotes the number of meshes from the magnetic field node to the interface between the absorption layer and the calculation region；
S402, initializing the distance from an electric field node in the absorption layer to the absorption layer and an interface; the four types of electric field nodes have two distances to the interface between the absorption layer and the calculation region, wherein the distances are rho e，1 (k)＝kΔi，ρ e，2 (k)＝(k-0.5)Δi，ρ e，1 (k)、ρ e，2 (k) Represents the distance of the electric field node from the interface of the absorption layer and the calculation region, wherein k represents the number of grids from the electric field node to the interface of the absorption layer and the calculation region.
5. A method for calculating the electromagnetic radiation in the human brain with high accuracy according to claim 1, wherein: the step S5 includes:
s501, setting a time step length delta t, wherein n is the number of iteration steps at the current moment, updating magnetic field values in a calculation area and an absorption layer at the moment of (n +0.5) delta t, and aiming at a first-class magnetic field node H 1 The iterative calculation formula is calculated as follows:
where μ is the magnetic permeability,
and
depends on the magnetic field node H in the FCC grid 1 The node distribution mode of the electric field surrounding the periphery;
four types of magnetic field node H 1 ～H 4 Only the difference of the corner marks exists in the calculation iteration formula of (1), and for H 2 ～H 4 When performing the iteration, according to H 1 The calculation method of (2) is carried out, and the lower corner mark is replaced;
s502, after updating the magnetic field values in the calculation area and the absorption layer, updating the magnetic field of the absorption layer again; when the absorption layer is arranged in the x direction, H in the absorption layer in the x direction needs to be adjusted y ，H z Carrying out updating calculation; when the y-direction is provided with the absorption layer, H in the y-direction absorption layer needs to be adjusted x ，H z Carrying out updating calculation; when an absorption layer is arranged in the z direction, H in the absorption layer in the z direction needs to be adjusted x ，H y Performing update calculation according to a given magnetic field node;
absorption layer magnetic field node H 1 ～H 4 Only the difference of the corner marks exists in the calculation iteration formula of (1), and the node H is used for the first type of magnetic field 1 The iterative calculation formula is calculated as follows:
kappa is an absorption layer parameter; for H in the absorption layer 2 ～H 4 According to H 1 The calculation method of (2) is carried out, and the subscript is replaced during calculation,
and
is a suction tubeNode H in the collector for the first type of magnetic field 1 Iteratively updating the process quantity; h in the absorption layer 2 ～H 4 The process quantity of the iterative update is
According to the marked coordinates of the magnetic field nodes and the surfaces from the magnetic field nodes to the absorption layer and the calculation area respectively, the magnetic field nodes are calculated
Divided into two classes and represented by rho m，1 And ρ m，2 Determining; in the absorption layer in the x-direction
And
from rho m，1 And the type of magnetic field node to determine,
and
from rho m，2 And magnetic field node type determination; in the absorption layer in the y-direction
And
from rho m，1 And the type of magnetic field node, and,
and
from rho m，2 And magnetic field node type blockDetermining; in the absorption layer in z-direction
And
from rho m，1 And the type of magnetic field node to determine,
and
from rho m，2 And magnetic field node type determination;
by rho m，1 Determined by a magnetic field node of the first kind
The calculation formula of (a):
wherein alpha is m，1 ，σ m，1 And kappa m，1 Is the absorption layer parameter and is represented by p m，1 The determination and calculation method are as follows
Wherein sigma max ，α max ，κ max And n cpml Is the absorption layer fixed constant, δ is the absorption layer grid number times this grid step;
due to the similarity of the way in which the calculations are made,
and
relative to
Only the orientation of the lower corner mark needs to be modified,
the calculation can be completed only by replacing the lower corner mark number;
s503, after the magnetic field is processed, updating electric field values in the calculation area and the absorption layer at the (n +1) delta t moment;
epsilon is a dielectric constant of the glass fiber,
and
is dependent on the way of calculationIn the FCC grid, the distribution mode of the magnetic field nodes surrounding the electric field nodes of the current iteration;
s504, after the electric field values in the calculation area and the absorption layer are updated, updating the electric field of the absorption layer again; magnetic field node types for two distances; when the absorption layer is arranged in the x direction, the absorption layer is required to be absorbed by E in the absorption layer y ，E z Carrying out updating calculation; when the absorption layer is arranged in the y direction, it is necessary to absorb E in the absorption layer x ，E z Carrying out updating calculation; when an absorbing layer is arranged in the z direction, it is necessary to absorb E in the absorbing layer x ，E y Carrying out updating calculation; for electric field node E of the first kind 1 The iterative calculation mode is as follows:
for the absorption layer E 2 ～E 4 According to the calculation mode of E 1 The calculation method of (2) and the substitution is carried out at the lower corner mark,
and
is a node E in the absorption layer for the first type of electric field 1 Iteratively updating the process quantity; in the absorption layer E 2 ～E 4 The process quantity of the iterative update is
Basis markThe coordinates of the nodes of the electric field and the interfaces from the nodes of the electric field to the absorption layer and the calculation region are calculated
Are divided into two classes and represented by rho e，1 And ρ e，2 Determining; in the absorption layer in the x-direction
And
from rho e，1 And the electric field node type decision,
and
from rho e，2 And electric field node type determination; in the absorption layer in the y-direction
And
from rho e，1 And the electric field node type decision,
and
from rho e，2 And electric field node type determination; in the absorption layer in z-direction
And
from rho e，1 And the electric field node type decision,
and
from rho e，2 And electric field node type determination;
by rho e，1 Determined by the nodes of the electric field of the first kind
The calculation formula of (a):
wherein alpha is e，1 ，σ e，1 And kappa e，1 Is the absorption layer parameter and is represented by p e，1 The determination and calculation method are as follows
Due to the similarity of the manner of calculation,
and
relative to
Only the orientation of the lower corner mark needs to be modified,
the calculation can be completed only by replacing the lower corner mark number;
s505, changing the time step from n time to n +1 time, outputting the current time step iteration result, and outputting the electromagnetic field value at the current time recording point, namely the electromagnetic radiation received by the human brain;
and judging whether the maximum value of the set iteration steps is reached, if not, returning to the step S501 to calculate the electromagnetic field value in a new round, and if so, stopping the calculation.
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Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1473268A (en) * | 2001-08-08 | 2004-02-04 | 株式会社Ntt都科摩 | Absorption power measuring device |
| CN102013895A (en) * | 2010-12-13 | 2011-04-13 | 惠州市硕贝德通讯科技有限公司 | Method for solving electromagnetic compatibility problem of antenna of minitype terminal mobile phone |
| CN102437410A (en) * | 2011-09-19 | 2012-05-02 | 惠州硕贝德无线科技股份有限公司 | Method for improving electromagnetic compatibility of mobile phone antenna and hearing-aid |
| CN102510296A (en) * | 2011-11-09 | 2012-06-20 | 中兴通讯股份有限公司 | Mobile terminal and method for reducing radiation of mobile terminal |
| CN108027412A (en) * | 2015-07-07 | 2018-05-11 | Q生物公司 | The constant Quantitative MRI Measurement characteristic indication in field |
| CN108136195A (en) * | 2015-10-26 | 2018-06-08 | 奥海视网膜科技有限公司 | The method for carrying out biological tissue's thermotherapy using the energy source of pulse |
| CN110998971A (en) * | 2017-05-23 | 2020-04-10 | 撒加德有限公司 | Radiation shield |
| WO2022031362A1 (en) * | 2020-08-04 | 2022-02-10 | Ojai Retinal Technology, Llc | System and method for preventing or treating alzheimer's and other neurodegenerative diseases |
-
2022
- 2022-03-18 CN CN202210272635.1A patent/CN114818412B/en active Active
Patent Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1473268A (en) * | 2001-08-08 | 2004-02-04 | 株式会社Ntt都科摩 | Absorption power measuring device |
| CN102013895A (en) * | 2010-12-13 | 2011-04-13 | 惠州市硕贝德通讯科技有限公司 | Method for solving electromagnetic compatibility problem of antenna of minitype terminal mobile phone |
| CN102437410A (en) * | 2011-09-19 | 2012-05-02 | 惠州硕贝德无线科技股份有限公司 | Method for improving electromagnetic compatibility of mobile phone antenna and hearing-aid |
| CN102510296A (en) * | 2011-11-09 | 2012-06-20 | 中兴通讯股份有限公司 | Mobile terminal and method for reducing radiation of mobile terminal |
| CN108027412A (en) * | 2015-07-07 | 2018-05-11 | Q生物公司 | The constant Quantitative MRI Measurement characteristic indication in field |
| CN108136195A (en) * | 2015-10-26 | 2018-06-08 | 奥海视网膜科技有限公司 | The method for carrying out biological tissue's thermotherapy using the energy source of pulse |
| CN110998971A (en) * | 2017-05-23 | 2020-04-10 | 撒加德有限公司 | Radiation shield |
| WO2022031362A1 (en) * | 2020-08-04 | 2022-02-10 | Ojai Retinal Technology, Llc | System and method for preventing or treating alzheimer's and other neurodegenerative diseases |
Non-Patent Citations (3)
| Title |
|---|
| 低强度微波辐射对脑组织和脑细胞影响的研究进展;张盛庆宇，李志强，舒逍;《职业与健康》;20210731;第37卷(第17期);2429-2432 * |
| 蜂窝移动通信基站电磁辐射对人体影响的探讨;王孟均等;《中国无线电》;20071126(第11期);38-41 * |
| 被试品辐射发射试验点位对测试结果影响;吕冬翔，苏东林;《北京航空航天大学学报》;20170131;第43卷(第1期);100-106 * |
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